The discovery and application of nuclear power is one of the most profound scientific accomplishments of the 20th century, beginning with tentative explorations of the structure of matter, expanding into a rapid succession of unexpected discoveries, and finally settling into a seamless transition from theoretical science to applied engineering. There were many changes to nuclear power during this century - science transitioned from an academic pursuit to an industry, the use of uranium changed from an occasional orange or green dye in ceramics to major power-fuel, and public safety concerns shifted from boiler explosions on steamboats to nuclear reactor explosions on continents.